QPOs from the Viscous Transonic Accretion Flow Around a Spinning Black Hole

TL;DR

This study models viscous accretion flows around spinning black holes to understand the dependence of QPO frequencies on black hole spin, matching observed phenomena in X-ray binaries.

Contribution

It introduces a pseudo-potential approach to analyze viscous shock oscillations and their relation to black hole spin and QPO characteristics.

Findings

QPO frequency range depends strongly on black hole spin.

Low-spin black holes show low-frequency QPOs.

High-spin black holes produce a broad QPO frequency spectrum.

Abstract

We investigate the dynamics of transonic advective accretion flows around spinning black holes in the presence of viscosity. The spacetime of a Kerr black hole is approximated using a pseudo-potential. We study viscously driven shock oscillations over a range of black hole spin parameters. Our results show that the frequency range of quasi-periodic oscillations (QPOs) obtained from the power density spectra depends strongly on the black hole spin. Low-spin systems predominantly exhibit low-frequency QPOs, whereas rapidly rotating black holes (0.9) produce QPOs spanning a broad range from low to high frequencies, comparable to those observed in black hole X-ray binaries. We further obtain a correlation between the QPO frequency and the power-law photon index by computing the spectrum for a 10 solar mass black hole.